Koster, Cornelis H. A. (25–28 June 1996). "The Making of Algol 68". In Bjørner, Dines; Broy, Manfred; Pottosin, Igor V. (eds.). Perspectives of System Informatics: Second International Andrei Ershov Memorial Conference, Proceedings. Lecture Notes in Computer Science. Vol. 1181. Akademgorodok, Novosibirsk, Russia. pp. 55–67. doi:10.1007/3-540-62064-8_6. Especially see p. 61.
Koster, Cornelis H. A. (25–28 June 1996). "The Making of Algol 68". In Bjørner, Dines; Broy, Manfred; Pottosin, Igor V. (eds.). Perspectives of System Informatics: Second International Andrei Ershov Memorial Conference, Proceedings. Lecture Notes in Computer Science. Vol. 1181. Akademgorodok, Novosibirsk, Russia. pp. 55–67. doi:10.1007/3-540-62064-8_6. Especially see p. 61.